The present invention relates, generally, to sheet diverters for directing sheets moving in serial fashion along a path to one of a plurality of collation paths and, more particularly, to a high speed sheet diverter of the foregoing kind for collation of printed signatures to be used in the binding of a publication such as a magazine or a newspaper. The present invention further relates to an improved diverter assembly for collating sheets, such as signatures, from a high speed printing press. Specifically, the present invention provides a sheet diverter with diverter rolls and a diverter wedge positioned therebetween, the function of which is to allow for faster operating machine speeds with fewer jams and, at the same time, to improve the collation process such that the quality of signatures is improved as the signatures move along one of a plurality of collation paths.
Sheet diverters may range from the collating apparatus associated with an office copier, to sheet or web handling devices employed in the manufacture of paperboard articles, to sheet diverters specifically adapted to collate signatures to be used in binding or otherwise assembling books, magazines or newspapers. Each of these environments presents a somewhat different challenge in designing an efficient diverter or collator, but the same objective applies to the entire class of apparatus, namely, accurately routing selected flexible webs or ribbon sections along a desired collating path to achieve a desired order.
In the printing industry, an image is repeatedly printed on a continuous web or substrate such as paper. The ink is dried by running the web through curing ovens. In a typical printing process, the continuous web is subsequently slit (in the longitudinal direction which is the direction of web movement) to produce a plurality of continuous ribbons. The ribbons are aligned one on top of the other, folded Longitudinally, and then cut laterally to produce a plurality of multi-paged, approximately page length web segments, termed signatures. A signature can also be one printed sheet of paper that has or has not been folded. It is often desirable to transport successive signatures in different directions or paths. In general, a sheet diverter operates to route a signature along a desired one of a plurality of paths.
A sheet diverter in a folder towards the end of a printing press line must be operable at the high speeds of the press line, typically in excess of 2,000-2,500 feet per minute (fpm). It is desirable to run both the press, folder and other equipment in the printing press line at the highest speed possible to produce as many printed products as possible in a given amount of time. However, the physical qualities of printed paper or similar flexible substrates moving at a high rate of speed can result in undesirable whipping, dog-earring, tearing, smearing of the ink, or bunching of the substrate. Additionally, impact between the leading edge of a signature and a diverter wedge may result in the leading edge of the signature being dented or dog-eared or damaged in other ways. Moreover, the trailing edge of a signature may slap against the top edge of a diverter wedge, resulting in tears, dog-ears or other damage to the trailing edge. Damaged signatures may be of reduced or unacceptable quality and may also lead to jams in the folder, resulting in downtime, repair expense and much wasted paper.
Another problem which occurs when operating a press and a folder at high speeds is that signatures may be routed to an undesired one of a plurality of collation paths. As the leading edge of a signature approaches the apex of a diverter wedge, depending on the stiffness of the signature and due to the relationship between the diverter and the diverter wedge, the signature may be delivered to the wrong side of the diverter wedge thereby sending the signature down the wrong collation path. This leads to jams in the folder causing delays and expense.
Yet another problem when operating a printing line at high speeds concerns ink offset in the diverter. As a signature impacts a diverter wedge, non-dried ink may transfer to the surface of the diverter wedge. As successive signatures contact the diverter wedge, the ink transferred to the diverter wedge may undesirably pass to the other signatures. The greater the impact of the signatures against the diverter wedge, the greater the likelihood of ink offset.
Many of the foregoing defects become more prevalent above certain speeds of the printing press and folder. For example, such defects may occur when the press is run at speeds greater than 2,500 fpm, but may not occur when the press is run at a slower speed, for example, 2,200 fpm. As printing press speed capabilities have increased, it has become increasingly important to provide a system which allows for individual signatures to be directed down any one of a plurality of selected collation paths without damaging the leading or trailing edge of each signature or causing jams.
U.S. Pat. No. 4,373,713 discloses a diverter mechanism placed in a path of a stream of cut sheets comprising a pair of rotary diverters with raised cam surfaces used to divert and guide the sheets. A tapered guide has a pair of diverging guide surfaces and has its upstream tapered end interposed between the rotary diverters with raised cam surfaces and diverging tapes.
A sheet diverter for signature collation and a method thereof is described in U.S. Pat. No. 4,729,282, assigned to Quad/Tech, Inc., of Pewaukee, Wis., and is hereby incorporated by reference. The ""282 patent discloses a sheet diverter including an oscillating diverter guide member that directs successive signatures to opposite sides of a diverter wedge. As set forth in the ""282 patent, the diverter design disclosed in the ""713 patent is not viewed as workable in light of the high speeds sought to be attained nor is it seen to be particularly reliable in reducing jamming tendencies which are expected to arise in these settings.
Diverting devices are used in the printing industry to divert individual signatures along alternating paths in the folder part of a printing press line. Because the diverting operation has a slow processing velocity in relation to the rest of the line, the industry seeks to speed up this operation while reducing damage to the signatures and avoiding jams.
There is a need for a sheet diverter that is capable of operating at high speeds, e.g., in excess of 2,500-3,000 fpm and above, and yet also capable of providing a signature that is acceptable in quality. What is also needed is a sheet diverter for use in the printing industry such that the sheet diverter improves the collation process of printed signatures to prevent or minimize damage to the signatures as the signatures move along one of a plurality of collation paths to increase the quality of each signature, allow for greater operational speeds and reduce downtime and repair expenses associated with jams in a folder. What is further needed is a sheet diverter for use in a high speed printing press line which is designed to prevent or minimize the transfer of non-dried ink to a diverter wedge of the sheet diverter thereby enhancing the overall quality of the printed signatures.
In one embodiment of the present invention, a diverter assembly for diverting signatures from a diverter path to a desired one of a plurality of collation paths is provided. A pair of spaced apart, rotating diverter rolls have respective travel paths which define a common swipe path for the diverter rolls. A diverter wedge which separates the plurality of collation paths is positioned between the pair of diverter rolls such that a portion of the diverter wedge extends into the common swipe path. Positioning the diverter wedge in the common swipe path of the diverter rolls allows for increased control over signatures traveling through a folder as compared to prior known apparatus and methods thereby allowing for greater operational speeds, decreasing signature damage, less ink offset to the diverter wedge and reducing jamming tendencies in a folder.
In another embodiment of the present invention, a sheet diverter for diverting signatures delivered from a printing press to a selected one of a plurality of collation paths is provided. The sheet diverter includes an oscillating diverter device for directing a leading edge of a signature to one of the plurality of collation paths. The sheet diverter also includes a diverter which separates the plurality of collation paths for deflecting a signature to a selected one thereof. The oscillating diverter device and the diverter are capable of intermeshing at appropriate times so as to increase control over signatures traveling through a folder as compared to prior known apparatus and methods thereby also allowing for faster operational speeds, decreasing signature damage, less ink offset and reducing jamming tendencies in a folder.
In yet another embodiment of the present invention, a method for collating signatures delivered from a high speed printing press is provided. A signature is delivered to a pair of oscillating diverter rolls which generally translate over a reciprocable path which is generally normal to the path of the signatures. The translation of the diverter rolls with respect to a diverter wedge positioned therebetween is such that damage to the signatures is substantially minimized or prevented as the signatures travel to and past the diverter wedge thereby allowing for increased operating speeds with fewer jams. The translation of the diverter rolls is properly timed or adjusted with respect to the approach or position of the signatures in relation to the diverter rolls.
Accordingly, it is a feature of the present invention to provide an apparatus and a method thereof that minimizes the potential for damage to signatures as they travel down one of a plurality of collation paths, while also allowing for increased operating speeds.
Another feature of the present invention is to provide a sheet diverter in a printing press operation that provides for improved collation of signatures therethrough while eliminating the need for expensive, complicated equipment as is currently used in the industry. Thus, a feature of the invention is to provide a simple, inexpensive device to improve the collation process in a sheet diverter of a printing press and folding operation.
Yet another feature of the present invention is to provide a diverter in a printing press capable of operating at excessive speed, e.g., in excess of 2,500-3,000 fpm and above, and yet also capable of producing signatures of acceptable quality standards, while at the same time reducing jams which would normally occur in prior known devices if such devices were operated at the contemplated rates of speed discussed herein, all of which thereby minimizes machine downtime and repair expenses, and increases product output over a specified period of time.